In desktop or other office and related type staplers, an anvil operates below a stack of papers to bend staple legs behind the paper. Such clinching binds the papers together. A typical anvil is made of a hard steel plate including two adjacent arcuate depressions. During the stapling process, the staple legs enter an outer portion of the depressions and slide within the depressions to form a rounded or looped clinch. The legs are formed at the same time that the staple is being ejected from the stapler. This system is simple and normally effective for binding papers. However, the looped legs protrude from the face of the backside of the paper stack. As a result, the stack becomes thicker at the location of the staple. When multiple stapled paper stacks are stored together, as in a file cabinet, folder, or binder, the corners with the looped staples fan out whereby the adjacent stack is pushed away by the staple loop at the corner. The capacity of document storage thus becomes reduced.
Forming the loop also uses excess extra energy since the wire is bent upon an extended portion of its length. Further, the maximum thickness of a paper stack is limited since a very short leg segment cannot be looped. For example, a loop type form with a standard 26/6 staple may be limited to about 30 sheets of 20 lb. paper in a best case.
Another type of clinch is of a flat configuration. The staple leg remains relatively straight as it is bent behind the stack. An advantage of this design is a more compact assembly of stacks. The staple legs are substantially parallel and adjacent to the backside paper face whereby adjacent stacks can rest very near to each other at the staple location. An assembly of flat clinched stacks thus is more compact in storage than that of looped staple stacks. The straight segment may allow binding up to 40 sheets with a high quality standard size staple. Further, to some consumers, a flat clinch is of better appearance than a loop type.
A typical flat clinch design operates in two distinct stages. In a first step the staple is ejected from the stapling device. The staple legs are pushed through the papers to extend from the backside straight out or partially pre-bent by an element of the anvil. A second step has the legs being fully bent against the stack backside by an externally powered component. According to this procedure, the bending step must be timed in relation to the first ejection step through a timing action external to the base. Therefore, the staple ejecting mechanism, for example, in the main body portion of a desktop stapler, must be operatively linked to the base portion that includes the anvil. In the case of a manually-operated stapler, for example, the second step starts at a predetermined position of the handle with a conspicuous clunk. Further, this linkage is mechanically complex. Such connection also normally precludes an option to open the base away from the body for use as a tacker since the body and base are tied together by this flat clinch linkage. An electric powered stapler similarly requires complex linkages in typical flat clinch designs to link the motor to the secondary clinching action. It is therefore desired to have a flat clinch stapler with a simplified design wherein the clinching action is enabled primarily or entirely within the base.